Evaporant material control for vapor deposition apparatus



Jan. 6, 1970 R. G. LINS 3,483,214

- EVAPORANT MATERIAL coumor, FOR VAPOR DEPOSITION APPARATUS 'Filed March 15, 196? 2 Sheets-Sheet 1 I6 I8 20 22 24 ll "HI! 50 52 32 X a VAR. SPEED VAR. SPEED Z Y wms FEED 1 was FEED MOTOR v MOTOR 44 2a 30 VARSPEED CHOPPER I MOTOR 34 Fig. I

INVENTOR RAYMOND 6. Ll/VS ATTO Y Jan. 6, 1970 I (5, s 3,488,214

EVAPORAN'IYMATERIAD CONTROL FOR VAPOR DEPOSITION APPARATUS Filed March 15. 1967 2 Sheets-Sheet 2 \:i I I l l 68 Fig. 3

V NH 9a 7 INVENTOR RAYMOND 6'. L/IVS BY 0ft ATTORNEY Q United States Claims ABSTRACT OF THE DISCLOSURE A device for the inethod of reducing the to-be-deposited materials of a vapor deposition apparatus into small bits that are to be vaporized upon contacting a heat source.

BACKGROUND OF THE INVENTION The present invention is directed toward that field of art that relates to the vapor deposition of a layered element of several Angstroms (A.) in thickness upon asubstrate member. The material that is to be deposited upon the substrate member is vaporized on contact with a heat source, which vapor is then directed upon the substrate member. The present invention is, in its preferred embodiment, particularly directed toward a vacuum deposition system that may be termed a wire feed on a refractory post method. In such a vapor deposition system the material that'is to be deposited upon the substrate member, such as Ni-Fe Wire, is fed at a variable rate on a heated tungsten post. The wire is substantially instantaneously vaporized thereby, except for short term fractionation, producing a vapor of substantially the same material composition as that desired in the layered element, e.g., 81.5% Ni-18.5% Fe in a substantially nonmagnetostrictive thin-ferromagnetic-film utilized as a memory element in electronic data processing equipment. The text Thin Film Microelectronics, L. Holland, ed., John Wiley and Sons, Inc., 1965, particularly chapter 4, provides some excellent background material for some prior art vacuunif deposition apparatus and techniques.

Alternatively, such a system may utilize a main Wire of a small magnetostrictive characteristic of a negative sense-82% Ni-l8'% Feand compensate for the nickelrich main-Wire-produced-vapor by utilizing a secondary wire of a small magnetostrictive characteristic of the opposite sensee.g., positive magnetostriction. The main wire is then utilized to provide a continuous vapor with the varying feed of the secondary wire varying the material composition of the layered element to that producing the desired magnetostriction. The method provides a substantially uniform material composition throughout the layered element thickness, and, consequently, provides a simple method for producing layered elements of various thicknesses with all thicknesses having a substantially zero magnetostrictive characteristic as is desired in a magnetizable memory element. The copending patent application of P. E. Oberg et al., Ser. No. 332,220, filed Dec. 20, 1963, now Patent No. 3,336,154 and assigned to the Sperry Rand Corporation as is the present invention, discusses an apparatus for monitoring the varying material composition of the so-generated deposited layer so as to provide a means for controlling the relative percentages of the constituent materials thereof.

In the publication An Automated Experimental Vacuum Deposition System, D. A. Tandeski et al., Vacuum, vol. 14, pp. 36 there is disclosed one prior art method of achieving a vacuum deposition system utilizing the above disclosed wire feed on a tungsten post method. In this arrangement the to-be-deposited material, in the'form of a wire of a known composition, is fed onto 3,488,214 Patented Jan. 6, 1970 one surface of an electron-bombardment-heated refractory block from which evaporation takes place. The block, such as a tungsten post, is an electrical conductor and operates at a temperature considerably higher than the melting point of the wire source material Without significantly alloying with the evaporant and without a significant vapor pressure of its own constituents. The wire source material is fed onto the upper surface of the heated block by means of a friction drive through a guide tube that directs the wire onto the block surface at approximately a 45 angle. However, with the wire source material contacting the heated post at a fixed point on its surface excessive alloying of the block surface occurs changing the surfaces physical characteristics, which change may'alter the composition and path of the evaporant.

SUMMARY OF THE INVENTION The present invention is directed toward an apparatus and a method of overcoming the excessive alloying, or erosion, of the heated tungsten block, and, accordingly, to provide an improved vacuum deposition system whereby the composition of the evaporant is maintained at the desirable equilibrium condition. The present invention involves a device for and a method of reducing the to-bedeposited materials of a vapor deposition apparatus, such as a Permalloy wire of 0.015 inch diameter, into small bits approximately 0.010-01015 inch in length that are to be vaporized upon contacting a heated tungsten post that is driven by a power source of several hundred watts (w.). The bits of the to-be-deposited materials are distributed uniformly and controllably over the entire surface of the heated tungsten post to provide complete, as well as uniform, evaporation for a uniform tungsten post temperature. By providing a uniform distribution of the hits over the entire surface of the heated tungsten post, changes over the surface of the heated tungsten post occasioned by the prior art method are eliminated whereby complete and uniform evaporation of the bits is achieved. Additionally, by using two material seurces as in the above discussed copending patent application of P. E. Oberg et al. the composition of the evaporant may be continuously controlled'over a wide range of relative material compositions.

As stated above, the prior art method is subject to short term fractionation which tends to produce layered elements of nonhomogeneous materialtomposition. This deficiency is due to the fact that the alloy Wire feed on the heated tungsten post is at a constant rate. When the alloy wire contacts the heated tungsten post it melts and vaporizes, but tends to melt back up the wire. Although the Wire is being fed at a constant rate, it is not then in immediate contact with the heated tungsten post providing a noncontinuous source, or replenishment, of the evaporant. Soon the wire again contacts the heated tungsten post, in the same place, and the process repeats itself. This intermittent replenishment of the evaporant tends to vary the deposition between high and low rates. Further, the evaporant tends to be iron-rich during the high deposition rate and nickel-rich during the low deposition rate. This short term fractionation further increases the nonhomogeneous nature of the material composition of the layered alloy element. In contrast, the present invention, by providing a constant source of a substantially homogeneous mixture of small bits of the alloy wire material, maintains an evaporant of a substantially constant deposition rate and material composition. This is so as each separate bit of the mixture acts as a separate material source, each at a particular instant in time evaporating in a different part of the iron-rich and nickel-rich phase providing a statistically uniform evaporant,

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration of a preferred embodiment of the present invention.

FIG. 2 is a side sectional view of the wire feed mechanism of the present invention.

FIG. 3 is a top sectional view of the wire feed mechanism of the present invention taken along line 3-3 of FIG. 2.

FIG. 4 is a side sectional view of the wire chopper mechanism of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With particular reference to FIG. 1 there is illustrated a preferred embodiment of the present invention. In this embodiment generation of the film elements is accomplished in an evacuatable environment. Such apparatus may comprise bell jar 10 mounted on a supporting base 12 sealed at a rim 14 between the jar 10 and the base 12. A vacuum pressure of approximately 10 torr or less is maintained within jar by any suitable well-known means. As the vacuum deposition system that is utilized by a wire feed on a refractory post method is considered well known, such as exemplified by the above referenced T. A. Tandeski et al. article, all equipment incident to such system but not essential to a description of the present invention is not illustrated.

The illustrated embodiment of the present invention as exemplified by FIG. 1 includes as wire sources two spools 16 and 18 containing the corresponding wires 20 and 22 each of a particular material composition as required by the material composition of the layered elements that are to be produced by the vapor deposition system of FIG. 1. Wires 20 and 22 are fed through their corresponding wire feed mechanisms 24 and 26, respectively, at a rate that is determined by their respectively associated variable speed wire feed motors 28 and 30'. Wire feed mechanisms 24 and 26 feed their associated wires 20 and 22, respectively, to wire chopper mechanism 32 that is driven by its associated variable speed chopper motor 34. Wire chopper mechanism 32 chops wires 20 and 22 into a plurality of relatively small bits at a rate that is determined by their associated wire feed mechanisms 24 and26. The relative percentages of the materials, making up each of wire 20 and wire 22, in the commingled bits of said wires 20 and 22 that are produced by wire chopper mechanism 32 is a function of the relative feed rates of wires 20 and 22 to chopper mechanism 32 as determined by the associated wire feed mechanisms 24 and 26.

The commingled bits of wires 20 and 22, as produced by wire chopper mechanism 32, are passed on to a chutelike means 36. Chute 36 conveys the commingled bits of wires 20 and 22 into funnel-like element 38 that is centered over the heated tungsten post 40 for obtaining a random and substantially homogeneous distribution of such commingled bits of wires 20 and 22 upon the top surface of such heated tungsten post. In order to prevent funnel 38 achieving a significantly high temperature whereby such commingled bits of wires 20 and 22 may become fused upon contact therewith there is provided about funnel 38 a coolant conveying means such as copper tubing 42 coupled to coolant source 44 whereby funnel 38 in its internal volume may be kept below a critical temperature preventing the fusion of the commingled bits of 20 and 22 upon disposal therein by chute 36. Above heated tungsten post 40 and its associated electron bombardment heating unit 46 there is provided a supporting means 50 for holding substrate means 52 and its associated aperture mask 54 which determines the planar contour of the thin-ferro-magnetic-filrn elements that are to be deposited upon substrate means 52.

With particular reference to FIG. 2 there is illustrated a sectional view of wire feed mechanism 24 (and 26) showing the driving means associated therewith. The driving means include two similar gear-like members and 62 having circumferential slots therein for conforming to the contour of wire 20. Wire 20 is maintained in a constant gripping pressure between gears 60 and 62 by means of spring means 64 providing a constant pressure on gear 62 for providing a substantially constant pressure upon wire 20 by gears 60 and 62. Wire 20 passes through top aperture 66 in body member 68 through the meshing cylindrical channels around the pheriphery of gears 60 and 62 and exits through aperture 70.

With particular reference to FIG. 3 there is illustrated a sectional plan view of wire feed mechanism 24 taken along plane 3-3 of FIG. 2. This view is illustrated to particularly point out the cylindrical-like grooves 61 and 63 around the pheripheries of gears 60 and 62 that are specifically designed to conform to the contour of wire 20 whereby spring 64 may provide a constant driving pressure upon the wire 20 that passes therethrough. Gear 60 is the driven member being mounted on driving shaft that is coupled, by any suitable driving means, to its associated variable speed wire feed motor 28. Gear 62 functions as an idle gear revolving about shaft 82 mounted in a guide slot 84 through body member 68 whereby the pressure applied by spring 64 causes gear 62 to provide a constant pressure upon wire 20 between it in gear 60 and located within slots 61 and 63 of the associated gears 60 and 62, respectively.

With particular reference to FIG. 4 there is illustrated a side sectional view of wire chopper mechanism 32. Wirechopper mechanism 32 consists of a main body portion having a cavity 92 along a first end with a cylindrical cavity 94 designed to form a close tolerance fit with drill 96 which passes through aperture, or cavity, 92 and is supported on its driven end by bushing retaining means 98. Drill, or cutter, 96 is driven in a rotary manner by a driving means 100 that couples the rotary action of variable speed chopper motor 34 to drill 96. Within body member 90 and normal to the longitudinal axis of drill 96 are two holes 102 and 104 permitting contact of the associated wires 20 and 22, respectively, with the cutting faces of drill 96. Rotation of drill 96 by means of its variable speed chopper motor 34 with wires 20 and 22 fed into their associated holes 102 and 104, respectively, by their associated wire feed mechanisms 24 and 26, respectively, causes the cutting faces of drill 96 to cut such wires 20 and 22 into relatively small bits. The relative quantities of the mixture of the sochopped bits of wires 20 and 22 are a function of their feed rate as determined by the relative speeds of their associated wire feed mechanisms 24 and 26, respectively. The commingled bits of wires 20 and 22 are drawn out into cavity 92 by the rotary action of drill 96 whereupon such commingled bits are allowed to fall within chute 36see FIG. 1.

As stated above the present invention involves a device for a method of reducing the tome-deposited materials of a vapor deposition apparatus, such as a Permalloy wire, into small bits that are to be vaporized upon contacting a heated tungsten post. By means of the present invention the bits of the to-be-deposited material are fed upon the heated tungsten post in a uniformly distributed manner over the entire surface of the heated tungsten post providing thereby a uniform evacuation of the bits of the to-be-deposited material. The method of the present invention is in contrast to the prior art method whereby the material that is to be deposited upon the substrate member, such as a Permalloy wire, is fed at a variable rate directly onto the heated tungsten post. As the wire source material is fed upon the upper surface of the heated tungsten post through a guide tube that directs the wire onto the same point of the post surface there is induced at this fixed point on the heated tungsten posts top surface, excessive surface alloying of the tungsten post whereby its physical contour at such fixed point may be considerably altered. This altering of the tungsten posts surface characteristics induces a change in the composition of the metallic vapor produced by the vaporized wire material, and also alters the manner and direction by which the metallic vapor is directed upon the surface of the substrate member upon which the metallic vapor is to be deposited.

Thus, it is apparent that there has been described and illustrated herein a preferred embodiment of the present invention that provides an improved method for the fabrication of layered elements in an evacuatable enclosure utilizing a modification of the wire feed on a refractory post vacuum deposition method. Having now, fully illustrated and described my invention what I claim to be new and desire to protect by Letters Patent is set forth in the appended claims.

What is claimed is:

1. A method of reducing the to-be-deposited materials of a vapor deposition apparatus into small bits that are to be vaporized upon contacting a heat source, comprismg:

feeding a material to a chopper mechanism at a determinable feed rate;

chopping said material into a plurality of small bits at a rate determined by said feed rate;

distributing said plurality of small bits over the surface of a heatedelement;

vaporizing said plurality of small bits upon contact with said heated element; and

depositing said vapor upon a substrate member.

2. The method of claim 1 wherein said determinable feed rate is variable.

3. A method of reducing to to-be-de-posited materials of a vapor deposition apparatus into small bits that are to be vaporized upon contacting a heat source, comprismg:

feeding a first wire of a first known material composition to a wire chopper mechanism at a determinable first feed rate;

feeding a second wire of a second known material composition to a wire chopper mechanism at a determinable second feed rate;

chopping said first and second Wires into a plurality of small bits at a rate determined by each of said wires associated feed rate;

commingling the plurality of small bits of said first and second wires forming a homogeneous mixture:

distributing said mixture over the surface of a heated element;

vaporizing said mixture upon contact with said heated element; and,

depositing said vapor upon a substrate member.

4. The method of claim 3 wherein said first and second feed rates are separately variable.

5. The method of claim 3 wherein said first and second feed rates are separately variably controllable for varying the relative percentages of the materials of said first and second wires in said mixture.

6. A device for reducing the to-be-deposited material of a vapor deposition apparatus into small bits that are to be vaporized upon contacting a heat source, comprismg:

a wire chopping mechanism;

a first wire feed mechanism for feeding a first wire to said wire chopping mechanism at a first feed rate for causing said wire chopping mechanism to chop said first wire into a plurality of small bits at a rate determined by said first feed rate;

a heat source having a heated surface; and

means for distributing said plurality of small bits over said heated surface for causing said bits to vaporize upon contact therewith.

'7. The device of claim 6 further including:

a second wire feed mechanism for feeding a second wire to said wire chopping mechanism at a second feed rate for causing said wire chopping mechanism to chop said second wire into a plurality of small bits at a rate determined by said second feed rate.

8. The device of claim 7 further including:

means for commingling the plurality of small bits of said first and second wires forming a homogeneous mixture.

9. The device of claim 6 wherein said distributing means includes a funnel-like element centered over said heat source.

10. The device of claim 9 further including cooling means adapted to cooperate with said funnel-like element for preventing the fusion of said mixture therein.

References Cited UNITED STATES PATENTS 2,635,579 4/1953 Chadset 11849 2,914,643 11/1959 Fields et al. 118-49 X 2,996,412 8/1961 Alexander ...V 118-49 FOREIGN PATENTS 485,965 5/1938 Great Britain.

OTHER REFERENCES Powell et al.: Vapor Deposition, copyright May 10, 1966, p. 272 relied upon.

ANDREW G. GOLIAN, Primary Examiner U.S. Cl. X.R. 11848; 219121 

